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We propose a MAC scheme for multirate wireless ad hoc networks, extending a power control algorithm called DPC/ALP (distributed power control with active link protection) (see Bambos, N. et al., IEEE/ACM Trans. on Networking, vol.8, no.5, 2000), which allows a mobile to predict its evolution of SIR by probing the channel for a short time. Using this property, we develop an access control scheme called adaptive probing which is capable of deciding the maximum allowable data rate. Contrary to CSMA schemes, which tend to wait for other mobiles to end their transmissions before initiating a new one, adaptive probing can selectively transmit at lower data rates in the presence of multiple active transmissions. As a result, it can lower the transmission delay even in heavily loaded networks, and performs better than standard approaches. Fairness is supported by a flow control mechanism called pipelining, which limits the number of consecutive transmissions of each user. Through a simulation study, we show that the proposed protocol can save power by more than 20 dB in a light network loading, and the delay in a heavy loading is smaller than a quarter of that of high rate IEEE 802.11b (11 Mbps).